Fluid driven systems have been previously devised for causing movement of a working member. It is common practice, for example, to manipulate a robot-like member by rotating it and/or moving it in a linear direction using pneumatic or hydraulic drive systems. An apparatus that uses pneumatics for rotary and linear motion is disclosed in Thompson U.S. Pat. No. 3,815,479, issued Jun. 11, 1974, and entitled "Compound Motion Fluid Actuator." This apparatus includes a rack gear and a rotary gear for converting linear motion to rotary motion. This rotary actuator is driven by means of fluid pressure whereby linear movement of the rack gear causes the rotary gear to rotate. A power cylinder is attached to the rotary actuator and includes a hollow piston rod that extends beyond the end of the cylinder. A guide rod telescopically fits into the hollow piston rod for controlling rotation while permitting linear movement of the piston. The guide rod is interconnected to the rotary gear so that rotary motion of the rotary gear is imparted to the guide rod. Because of this construction, the power cylinder can only be joined to the rotary actuator in one configuration, i.e., with the length of the power cylinder being substantially perpendicular to the length of the rotary actuator. There is no modular relationship between the rotary actuator and the power cylinder in that this actuator requires these two major components to be connected in only one way due to the relationship between the hollow piston rod, the guide rod and the rotary gear.
A further embodiment of an actuator apparatus that includes compound motion is apparently available through the Leen Company of Portland, Me. This apparatus is exemplified in Burke U.S. Design Pat. No. D308,207, May 29, 1990. With regard to the connection between the rotary actuator and the cylinder in this apparatus, a ball-spline sleeve is fixed to a pinion gear of the rotary actuator and a splined piston rod is provided in the ball-spline sleeve whereby the full stroke of the splined piston rod occurs with smooth, rolling linear movement. Additionally, the pinion gear is provided at one end of the rotary actuator so that direct drive is achieved close to the work being done. Like the compound actuator of the '479 patent, the rotary actuator and the cylinder can only be connected in one way.
With respect to mechanisms for coupling a rotating shaft to a machine element for imparting rotary motion to the element, such a mechanical unit is disclosed in Sousslloff U.S. Pat. No. 4,202,644, issued May 13, 1980, and entitled "Mounting Device." The disclosed device interconnects the cylindrical bore of the machine element to be rotated and a rotary shaft. The device has axially displacable sleeves that expand/contract to simultaneously grip the rotary shaft and the bore. The device further includes an internally threaded nut whereby rotation thereof allows axial displacement of the sleeves.
With respect to another embodiment of a rotary actuator for converting linear motion to rotary motion, the named assignee of the '479 patent has devised an air/oil tandem actuator having two cylinders and two rack gears. A rotary gear is operably connected to each of the two rack gears whereby controlled movement of a first rack gear in a first linear direction causes the rotary gear to rotate in a clockwise direction, while the other of the two rack gears moves linearly in a second direction, opposite that of the first rack gear. Conversely, counterclockwise rotation of the rotary gear is achieved by controlled movement of the second rack gear in the first direction. Relatedly, controlled movement of the second rack gear causes desired rotary movement of the rotary gear and accompanying linear movement of the first rack gear. Such controlled movement is accomplished using pressurized air. To provide smoother control of the rotary motion, this apparatus also includes hydraulic oil contained in each of the two tandem cylinders. When the racks are moved by pressurized air and there is accompanying rotary motion of the rotary gear, the contained oil acts to smooth the movement of the rack gears and thus the rotary gear. A reservoir is in fluid communication with the oil contained in the tandem cylinders and serves to compensate for oil volume changes due to temperature variation and leakage thereof. This reservoir is spaced from the tandem cylinders and requires a header pressure. Because of the required header pressure, the output port formed in the reservoir must be positioned below the reservoir for proper operation.